Smoke consists of particles of carbon in hot air and gases. These particles are mainly coated with organic acids and aldehydes. Use was widespread of synthetic materials (e.g. polyvinyl chloride) that release other substances, such as carbon monoxide and hydrochloric acid, on combustion. Respiratory symptoms may be immediate or delayed. Patients are dyspnoeic and tachypnoeic. Laryngeal stridor may require intubation. Hypoxia and pulmonary oedema can be fatal. Treatment is to remove the subject from the smoke and give oxygen. Intensive care may be required.